Tadalafil, Sildenafil, and Vardenafil are all polar small
molecules that are easily separated on the Unison UK-C18 HT column.
Not only are the slight structural differences between Sildenafil
and Vardenafil recognized by the column, but it also separates all
three compounds within 1.5 minutes.

The Scherzo SM-C18 and the Scherzo SW-C18 show similar
retention of these small molecules as the standard Unison UK-C18.
However, the Scherzo SS-C18 shows the best resolution between these
three compounds.

Both Scherzo SM-C18 and Scherzo SW-C18 can separate an
acidic compound (Ibuprofen) and a basic compound (Chlorpheniramine)
at the same time. Scherzo SW-C18 works better under gradient
elution, whereas Scherzo SM-C18 works better under isocratic
elution.

The effect of electrostatic interaction on retention.
Hydrophobic interaction, which depends on hydrogen bonding capacity
and dipole-dipole interaction, affects the retention time of
analysis on different columns.